An exhaust purification unit includes: a connecting pipe transmitting exhaust gas to a selective reduction catalyst (SCR); a urea water injection valve arranged to face an exhaust upstream end of the connecting pipe and injecting urea water into the connecting pipe; a mixer chamber forming a flow path along which exhaust gas flows from an exhaust downstream end of a front stage casing and turns back to the exhaust upstream end of the connecting pipe; and a flow adjustment member provided in the mixer chamber, being a member having a truncated-cone shape which extends from a vicinity of the injection opening of the urea water injection valve towards the connecting pipe with a diameter thereof gradually increasing, in which a plurality of small holes is formed, and in which a claw that guides the exhaust gas towards the exhaust downstream-side is provided for each of the plurality of small holes.

A process for detecting reductant deposits includes accessing data indicative of signal output from a radiofrequency sensor positioned proximate a decomposition reactor tube; comparing the data indicative of signal output from the radiofrequency sensor to a deposit formation threshold; and activating a deposit mitigation process responsive to the data indicative of signal output from the radiofrequency sensor exceeding the deposit formation threshold.

A multi-stage mixer includes a multi-stage mixer inlet, a multi-stage mixer outlet, a first flow device, and a second flow device. The multi-stage mixer inlet is configured to receive exhaust gas. The multi-stage mixer outlet is configured to provide the exhaust gas to a catalyst. The first flow device is configured to receive the exhaust gas from the multi-stage mixer inlet and to receive reductant such that the reductant is partially mixed with the exhaust gas within the first flow device. The first flow device includes a plurality of main vanes and a plurality of main vane apertures. The plurality of main vane apertures is interspaced between the plurality of main vanes. The plurality of main vane apertures is configured to receive the exhaust gas and to cooperate with the plurality of main vanes to provide the exhaust gas from the first flow device with a swirl flow.

A selective catalytic reduction (SCR) system is provided for treating exhaust gas in an exhaust passage. The system comprises a hydrolysis catalyst located in the exhaust passage, and a diesel exhaust fluid (DEF) dosing unit configured to inject DEF onto the hydrolysis catalyst. A SCR catalyst is located in the passage downstream of the hydrolysis catalyst, and a controller controls DEF dosing by the dosing unit. The controller is configured to control the DEF dosing unit such that the DEF is injected at a modulated frequency of less than or equal to 1 Hertz. A method of treating exhaust gas in an exhaust passage using an SCR system is also provided.

A method of treating exhaust gas in an exhaust passage using a selective catalytic reduction system is provided. The system comprises a hydrolysis catalyst in the passage upstream of a SCR catalyst, and a diesel exhaust fluid (DEF) dosing unit for injecting DEF onto the hydrolysis catalyst at a variable DEF dosing rate. The method comprises the steps of predicting an initial DEF dosing rate for converting all nitrogen oxide (NOx) contained in the exhaust gas, and estimating an amount of ammonia stored on the SCR catalyst. The method further comprises the steps of measuring a NOx conversion rate for the system, and adjusting the initial DEF dosing rate based upon the ammonia storage estimate and the measured NOx conversion rate to produce a first adjusted DEF dosing rate. An amount of ammonia-equivalent stored on the hydrolysis catalyst is then estimated, and the first adjusted DEF dosing rate is adjusted based upon the ammonia-equivalent storage estimate to produce a second adjusted DEF dosing rate. DEF is then injected at the second adjusted DEF dosing rate.

A reductant dosing system includes: an injector; a fixed displacement pump in fluid communication with the injector; a reductant source in fluid communication with the fixed displacement pump; a pressure sensor assembly configured to detect a pressure of reductant in the reductant dosing system; and a controller communicatively coupled to the fixed displacement pump and to the pressure sensor assembly, wherein the controller is configured to calculate a flow rate of the fixed displacement pump based on at least a calibration value determined based on data received from the pressure sensor assembly.

A reductant injecting device includes: a honeycomb structure comprising: a pillar shaped honeycomb structure portion having a partition wall that defines a plurality of cells each extending from a fluid inflow end face to a fluid outflow end face; and at least one pair of electrode portions arranged on a side surface of the honeycomb structure portion; an outer cylinder being configured to house the honeycomb structure, the outer cylinder having a carrier gas introduction port on the fluid inflow end face side; a urea sprayer arranged at one end of the outer cylinder; a carrier gas introduction cylinder provided at the carrier gas introduction port of the outer cylinder; and a carrier gas flow rate amplifier provided in the carrier gas introduction cylinder.

A reductant injecting device includes: a honeycomb structure comprising: a pillar shaped honeycomb structure portion having a partition wall that defines a plurality of cells each extending from a fluid inflow end face to a fluid outflow end face; and at least one pair of electrode portions arranged on a side surface of the honeycomb structure portion; an inner cylinder being configured to house the honeycomb structure; a urea sprayer arranged at one end of the inner cylinder; and an outer cylinder arranged on an outer peripheral side of the inner cylinder, the outer cylinder being spaced apart from the inner cylinder. A flow path through which the carrier gas passes is formed between the inner cylinder and the outer cylinder.

A system comprises a tank header configured to couple to a reductant tank and a heating mechanism positioned proximate to the tank header. The heating mechanism is configured to heat at least a portion of the tank header. The system may further comprise a conduit configured to pass reductant from the reductant tank and a junction configured to receive reductant from the reductant tank.

A decomposition reactor tube (DRT) for converting a reductant into ammonia includes an internal structure including a high-thermal conductivity material having a thermal conductivity greater than 20 W/(m.Math.K), wherein the internal structure is at least one of the splash plate, a splash plate frame, a double wall, an outer wall, a mixer, and/or an exhaust assist port.